1. Field of Invention
The present invention relates to a reference current source circuit and its system, and more particularly to a reference current source circuit without externally attached resistors and its system.
2. Description of Related Arts
Referring to FIG. 1, a conventional reference current source circuit is illustrated. The conventional reference depends on a resistor R31 and a reference current value thereof equals a reference voltage Vref of a reference voltage terminal divided by the resistance of the resistor R31, so the reference current value is related to an absolute value of the resistor. In semiconductor arts, an absolute value of a resistor can have a positive or negative deviation of 10%. Thus, in order to generate a highly precise reference current source, it is required to externally attach a resistor or to rectify the resistance value through a calibration mechanism of a back-end test, whereas both add up a cost of a chip.
Based on above analysis, the conventional reference current source needs an externally attached resistor to generate the highly precise reference current source and thus increases the cost of the chip.